The main function of the lens hood is to shade the lens from stray light, improving your contrast and image quality. But it will also protects the front barrel from the inevitable impacts against walls, door frames, and other real-life obstacles and in inclement weather, it can assist in keeping moisture or wind-blown debris off the lens. The advantage of the petal shape design is, that it offers the same prevention of flare as the corresponding circular or rectangular design, but with a smaller size and a lighter weight.
* Rotate lock-ring to expose the thread's mounting thread * Attach the hood by screwing it on the filter or lens thread. * Rotate lock-ring back to fix the hood on the thread. * While fixating the hood with the lock-ring, keep the " " symbol on the hood exactly at 12 o'clock position for the correct perpendicular orientation of the higher sides of the hood.